Assessment (as of 29 November 2018):
- In the past month or so, the central and eastern equatorial Pacific warmed significantly with sea surface temperature exceeding the normal range in October 2018. Based on the latest oceanic observations as well as forecasts by a number of climate models around the world, the central and eastern equatorial Pacific is likely to remain warmer than normal in the coming months, developing into an El Niño near the end of this winter (December 2018 – February 2019). Based on statistical analysis, the chance of normal to above-normal temperature in Hong Kong in winter is slightly higher during El Niño while the chance of normal to above-normal winter rainfall in Hong Kong is higher.
- Besides, under the influence of global warming and local urbanization, winter temperatures in Hong Kong exhibit a significant long-term rising trend. The chance of normal to above-normal temperature is generally higher. Climate models around the world forecast weaker-than-normal northeast monsoon over southern China this winter and hence above-normal temperature over the region is expected.
- Although the overall winter temperature in Hong Kong is
expected to be normal to above normal, day-to-day fluctuations
in weather and temperature could still be quite large with
occasional cold weather. However, under the influence of El
Niño, the chance of occurrence of cold weather in Hong Kong this
winter would be less than that of last year. Please refer to the
latest assessment provided by the local weather forecast and the
9-day weather forecast issued by the Hong Kong Observatory.
(Cold weather refers to temperature falling to 12°C or below. On average, there are 17 cold days per year. During last winter, there were a total of 21 days of cold weather.)
- In winter, El Niño affects the atmospheric circulation over the northern part of the South China Sea, bringing generally more rainfall to the coastal region as compared to the ENSO-neutral state. Climate models around the world also forecast similar circulation pattern for this winter, consistent with the situation during El Niño.
- Climate prediction centres around the world generate seasonal forecasts, employing a variety of methods including
dynamical models, statistical methods, expert judgment and combinations of them. Predictions from different centres do
not always agree and large discrepancies can occur at times. The Observatory adopts an ensemble approach to formulate
its seasonal forecast for Hong Kong, taking into consideration available products from major climate prediction centres
and the Global-Regional Climate Model (G-RCM) operated in house. Thus,
the resulting forecast issued by the Observatory may be different from the forecast given by G-RCM.
- The Observatory gratefully acknowledges the Tokyo Climate Center of the Japan Meteorological Agency and the National
Centers for Environmental Prediction of National Oceanic and Atmospheric Administration, USA for providing dynamical
prediction model forecast and hindcast data to support the formulation of seasonal forecast for Hong Kong.
- Forecast for spring 2019 (March to May 2019) will be available around 1st
Seasonal forecast charts provided by G-RCM and major climate centres: